Method of making aircraft propellers



y 9, 1935. s. H. SMITH METHOD OF MAKINQ AIRCRAFT PROPELLERS Filed July 28, 1931 m E N R O T T A -Pet nted my 9, 1935 V V V 2 007,775

' f Samuel 'sriiit li, Rocky, River, Ohio, assignor,

' by mesjne assignments; toAyiationManu fac turing'Corpoi-ation, ChicagoJlL, a corporation f; {Application-July er; 1931, Serial No. 553,521

. e s-8. a invention,relatesjto aircraft propellers, iaoeS an et."f rmsthe Outside es ate at the mmm .Pa rly,.totheconstructionand trailing edge. ls;

. method of making hollow metallic blades for such A blade has:-

h e i been shaped and'the tw o propellers. v sections-haverbeenrwelded togthehtheblade'is .5 'Anobjectis to providemeansiortheproduc- "suspended by the'lug iiionanchoringmeansina I tion of a hollow propeller blade which is formed .h a dsr m ."withtli p rt re-1 a f t eme from metallicblanks a nd possesses such strength wli, directly injline with the centers of'i gravityfof as will avoid the necesslty'of employing i t ri r the various cross sections of the blade, so that braces or webs. .while the blade is still in a hot condition the 10 .Another object is to provide means i'or' overheavier parts or the blade willtend to straighten to coming and eliminating any flaws or defects in thetip sections thereof. a the metallic structure of the blade which are v The next step in he man facture of the blade caused by excessive cold working." is provided in order to accurately align and pre- 1 While still another object is to provide means sely pet b d and o el nate ca se of for manufacturing a propeller blade formed and fl w in t me a by eliminating 001d Working- 18 aligned to a higher degree of precision and ac- A mold 9, avi two co r spond n sections curacy than in blades now in use. 7 20, clamp d to th b i e tu 2| c p- In the drawing, in which the preferred and crating with brackets 22, is provided with electric best known form of the invention is shown and h n elements Connected by Conductors 24. described: j V to a source of current. Any suitable heating go r Fig. 1 is a longitudinal section of the shaping means may be used to heat the mold l9, and it die showing the propeller mounted therein; 7 will be understood that I do not intend to limit Fig. 2 is a section on the line 2-4 of Fig; 1; my v nti n t h sp c fi heating m a s s wn Fig. 3 is an elevation view on the pressure face herein. 1 A 2 of the blade; and C The blade, which has been brought up to heat 25 Figs. 4, 5, 6, land 8 are enlarged sections taken trea ing p ra u e in the u nace, is' placed on lines 1-4, 5-5, 6-6, 1-1 and 8-8 respecin the hot mold l9, which hasbeen heated'by the tively of Fig. 3. V M electric heating elements 23, and the two sections I show my invention as applied to a propeller 20 of the. mold are clamped tightly together by blade ll, comprising a pressure face or thrust the studs 21.. e

face It, and a suction face or camber member l3, While the temperature in themold I9 is thus both of said faces terminating in a tubular shank maintained at the proper temperature by the portion H. The blade II is preferably formed electric heating elements 23, c mpressed air'is from two rolled. tapered metallic blanks, not introduced into the interior oi the blade ll, 3 shown herein, which are first placed in dies where through the shank I 4, by means of an air tube they are formed and cut to contour. The two 25, connected to'an air compressing means not cooperating portions or the blade are then held. shown herein, and secured to a closure member closely together in a jig, and are welded together 26 by a nut 2I. by any suitable means. To secure the best results, the temperature I 40 In this case, the weld is indicated by the dotted in the mold should be sufflciently high to cause 40 lines in Figures 1 and 3, and is shownin section the metal to be pliable and readily shaped, while in Figures 4 through 8. The tip of the blade H the air pressure should be high enough to exceed is provided with a lug l6 having an aperture l6a, the yield point of the metal at the parts requirand serving a purpose hereinafter explained. ing forming, a d Should be maintained 0 18 "It will be noticed, by-referring to sectional views enough to insure permanent setting or the metal. 43 4 through 8, that the weld I5 at the leading edge This p s of t ng metal and introducing i1, is positioned exactly at the point of interseccompressed air into the blade may be repeated tion of the two blade faces and, in fact, forms several times, and when'properly operated, will the edge portion along the leading edge. Furause all. part f h blade to be P p r y thermore, that the weld l5, at the trailing edge formed and li ned.

I8, is positioned solely withi'n-thesuction face From the foregoing, it will be apparent 'to l3 from the tip of the blade to substantially that those skilled in the art, that I have provided part of the blade shown in Figure 7, from which a method for manufacturing hollow metal propoint on to the end of the shank the weld is popeller blades from blanks joined by welding, sitioned at the'point of intersection of thetwo which is positioned where it will be subjected to 7 minimum stress and strain. Furthermore, beunderstood, that by heating the formed in a mold and introducing air pressure into the interior thereof, that great precision and accuracy of 'alignmentandformation is secured,

- and the proper thickness of the material through out the entire structure is At the same'time it will be apparent to those skilled in the art, that my invention includes advantages, uses and adaptations other than those mciflcally' pointed out or mentioned herein, and that my invention may be variously'changed, used or modified, all without departing from the spirit of my invention or sacrificing the advantages thereof. It, therefore, will be understood that the embodiment of'my invention herein set my invention is not welding said blanks sether by an inlaid metal weld between the contiguous edges of the blanks ,at the leadingedgeof the blade with the metal of weld disposed to-formthe leading edge throughout the eflective length of the blade, heating the blade teh'eat treating temperature, placing the heated blade in a heated mold, and introducing compres ed air into said blade while the blade is thus heated and held in the mold for producing an' accurately aligned Zamethodofmanufaoturing an aircraft propeller blade from two metal blanks each forming a face of the blade, shaping said blanks into a single blade with a tubular open-ended shank, welding said blanks together by an inlaid metal weld between the contiguous edges of the blanks at the leading edge with the metal of the weld disposed to form the leading edge throughout .the effective length of the blade and at the trailofthe blank forming the pressure face and the adjacent edge of the blank forming the suction face, heating the blade to heat treating'tem .perature, placing the 'heated blade in a heated mold, and introducing compressed air into said blade while the blade is thus heated and held in the mold for producing an accurately aligned blade. 7

r r SAMUEL E. SMITH. 

